98 



Scientific Proceedings (8i). 



60 (1238) 



The effects of ageing upon germ cells and their development. 

 By A. J. Goldfarb. 



[From the College of the City of New York, N. Y.] 



For several years experiments have been made with the germ 

 cells of the tropical sea urchins Toxopneustes and Hippanoe, and 

 the northern urchin Arbacia. The preliminary experiments were 

 made with a view towards obtaining experimental conditions 

 that were optimum and that gave the least variability for freshly 

 removed eggs and sperm from freshly collected sea urchins. Sur- 

 prisingly large differences were observed among the eggs from 

 different females. These differences involved (1) the size of the 

 eggs, (2) the presence of the jelly layer, (3) rate of membrane 

 formation, and (4) cleavage. 



By means of one or more of these criteria it was possible to 

 grade the different freshly collected females according to the 

 physiological condition of their eggs. Eggs of similar physiologic 

 condition showed a minimum variability and the highest correla- 

 tion with respect to these variants. 



When eggs and sperm were removed from their respective 

 bodies and kept under optimum laboratory conditions, the same 

 changes that had begun within the bodies of the sea urchins con- 

 tinued outside of the body. 



With increasing age outside of the body the eggs showed 

 progressive changes in size, in loss of jelly, in retarded membrane 

 formation, in decreased total cleavage and decreased rate of 

 cleavage, etc. And the exact degree of change in these regards 

 was ascertained for different intervals up to the death of the eggs. 



Still other changes were consequent upon ageing of the eggs, 

 which suggested the nature of the chemico-physical agencies in- 

 volved in the ageing process: namely, agglutination, fusion of two 

 or more eggs, separation of the blastomeres, and irregular cleavage. 



These changes suggested that the excess free HO ions in the 

 sea water was one agency and probably a very important one in 

 causing the dissolution of the jelly, the changes in permeability 

 of the cortical layer of the eggs, the changes in size, and all the 



